using System.Text.Json;

namespace AgentWikiUi.Core;

record ModelOption(string Label, string Id);

/// <summary>Esito di un messaggio: testo, id di sessione appreso dall'output (se il motore lo sceglie lui) o errore.</summary>
record EngineReply(string Text, string? SessionId, string? Error);

/// <summary>Un motore CLI (Claude Code, Codex): come si avvia, cosa si può scegliere, come si legge l'output. Vedi ADR-0002.</summary>
abstract class Engine
{
    /// <summary>Identificatore stabile, salvato nei JSON delle chat e usato da <c>--engine</c>.</summary>
    public abstract string Id { get; }
    public abstract string Name { get; }
    /// <summary>Etichetta sulle risposte ("Claude", "Codex").</summary>
    public abstract string Author { get; }
    public abstract string Executable { get; }
    public abstract ModelOption[] Models { get; }
    public abstract string[] Efforts { get; }
    /// <summary>True se l'id di sessione lo genera il motore e l'app lo legge dall'output.</summary>
    public abstract bool OwnsSessionId { get; }

    /// <param name="structured">true = GUI (output catturato e da interpretare); false = CLI (output ereditato).</param>
    public abstract List<string> BuildArgs(string prompt, string? sessionId, bool resume, string model, string effort, bool structured);
    public abstract EngineReply Parse(int code, string stdout, string stderr);

    public bool IsInstalled() => PathSearch.Find(Executable) is not null;

    protected string Failed(int code, string detail) => $"{Executable} è uscito con codice {code}\n{detail}".Trim();
}

sealed class ClaudeEngine : Engine
{
    public override string Id => "claude";
    public override string Name => "Claude Code";
    public override string Author => "Claude";
    public override string Executable => "claude";
    public override bool OwnsSessionId => false;

    // Da aggiornare quando escono nuovi modelli.
    public override ModelOption[] Models { get; } =
    [
        new("Fable 5.1", "claude-fable-5-1"),
        new("Opus 5.5", "claude-opus-5-5"),
        new("Sonnet 5.5", "claude-sonnet-5-5"),
        new("Haiku 5.5", "claude-haiku-5-5"),
    ];

    public override string[] Efforts { get; } = ["low", "medium", "high", "xhigh", "max"];

    public override List<string> BuildArgs(string prompt, string? sessionId, bool resume, string model, string effort, bool structured)
    {
        var args = new List<string> { "-p", prompt };
        if (sessionId is not null) args.AddRange([resume ? "--resume" : "--session-id", sessionId]);
        if (model != "") args.AddRange(["--model", model]);
        if (effort != "") args.AddRange(["--effort", effort]);
        return args;
    }

    public override EngineReply Parse(int code, string stdout, string stderr) =>
        code == 0 ? new(stdout.Trim(), null, null) : new("", null, Failed(code, stderr.Trim()));
}

sealed class CodexEngine : Engine
{
    public override string Id => "codex";
    public override string Name => "Codex";
    public override string Author => "Codex";
    public override string Executable => "codex";
    public override bool OwnsSessionId => true;

    // Il catalogo di Codex è dinamico (~/.codex/models_cache.json): elenco fisso, da aggiornare.
    public override ModelOption[] Models { get; } =
    [
        new("GPT-5.6 Sol", "gpt-5.6-sol"),
        new("GPT-5.6 Terra", "gpt-5.6-terra"),
        new("GPT-5.6 Luna", "gpt-5.6-luna"),
    ];

    public override string[] Efforts { get; } = ["low", "medium", "high", "xhigh", "max"];

    public override List<string> BuildArgs(string prompt, string? sessionId, bool resume, string model, string effort, bool structured)
    {
        var args = new List<string> { "exec" };
        var resuming = resume && sessionId is not null;
        if (resuming) args.Add("resume");
        if (structured) args.Add("--json");
        args.Add("--skip-git-repo-check");
        // `exec resume` non accetta -s: la sola lettura si impone con la configurazione
        if (resuming) args.AddRange(["-c", "sandbox_mode=\"read-only\""]);
        else args.AddRange(["-s", "read-only"]);
        if (model != "") args.AddRange(["-m", model]);
        if (effort != "") args.AddRange(["-c", $"model_reasoning_effort={effort}"]);
        if (resuming) args.Add(sessionId!);
        args.AddRange(["--", prompt]); // `--`: un prompt che inizia con "-" non è un'opzione
        return args;
    }

    // stdout è JSONL: thread.started (id), item.completed/agent_message (testo), turn.failed/error (errore).
    public override EngineReply Parse(int code, string stdout, string stderr)
    {
        string? threadId = null, lastMessage = null, error = null;
        foreach (var line in stdout.Split('\n', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries))
        {
            try
            {
                using var doc = JsonDocument.Parse(line);
                var e = doc.RootElement;
                switch (e.GetProperty("type").GetString())
                {
                    case "thread.started": threadId = e.GetProperty("thread_id").GetString(); break;
                    case "item.completed" when e.GetProperty("item").GetProperty("type").GetString() == "agent_message":
                        lastMessage = e.GetProperty("item").GetProperty("text").GetString(); break;
                    case "turn.failed": error = InnerMessage(e.GetProperty("error").GetProperty("message").GetString()); break;
                    case "error": error ??= InnerMessage(e.GetProperty("message").GetString()); break;
                }
            }
            catch (Exception ex) when (ex is JsonException or KeyNotFoundException or InvalidOperationException) { } // riga non JSON o evento sconosciuto
        }
        if (code != 0) return new("", threadId, Failed(code, error ?? stderr.Trim()));
        if (string.IsNullOrWhiteSpace(lastMessage)) return new("", threadId, error ?? "codex non ha restituito nessuna risposta.");
        return new(lastMessage.Trim(), threadId, null);
    }

    // L'errore arriva come stringa che contiene un JSON {"error":{"message":…}}: si mostra il messaggio interno.
    static string? InnerMessage(string? raw)
    {
        if (raw is null) return null;
        try
        {
            using var doc = JsonDocument.Parse(raw);
            return doc.RootElement.GetProperty("error").GetProperty("message").GetString() ?? raw;
        }
        catch (Exception ex) when (ex is JsonException or KeyNotFoundException or InvalidOperationException) { return raw; }
    }
}

static class Engines
{
    public static readonly Engine Claude = new ClaudeEngine();
    public static readonly Engine Codex = new CodexEngine();
    public static readonly Engine[] All = [Claude, Codex];

    public static Engine? Find(string? id) => All.FirstOrDefault(e => e.Id == id);
}

static class PathSearch
{
    // Su Windows i motori si avviano direttamente: solo .exe (niente script .cmd, vedi ADR-0002).
    public static string? Find(string name)
    {
        var file = OperatingSystem.IsWindows() ? name + ".exe" : name;
        foreach (var dir in (Environment.GetEnvironmentVariable("PATH") ?? "").Split(Path.PathSeparator, StringSplitOptions.RemoveEmptyEntries))
        {
            try
            {
                var full = Path.Combine(dir.Trim('"'), file);
                if (File.Exists(full)) return full;
            }
            catch (ArgumentException) { } // voce del PATH non valida
        }
        return null;
    }
}